1. Field of the Invention
The present invention generally relates to bypass plungers and more particularly to bypass plungers adapted through novel design features to control descent, extend useful life, and resist failures from loosening assemblies.
2. Background of the Invention and Description of the Prior Art
In the well bores constructed in subterranean formations to access deposits of oil and gas, fluids can build up and impede production of the oil and gas. One effective device frequently used to overcome this condition is to use a plunger apparatus that is configured to freely cycle upward and downward in the well bore. Such plunger devices are variously called gas lift plungers, differential pressure operated pistons, bypass plungers, auto-cycling plungers, and the like. The plunger is released into the well bore at the surface and allowed to fall toward the distal or bottom end of the well bore through fluid or gas that may be present in the well. At the end, pressure builds under it and causes the plunger to travel toward the surface, lifting the fluids ahead of it. As the plunger reaches the surface, the fluids are discharged, and the plunger is released to fall back into the well bore to, the distal or bottom end to repeat the cycle. The cycle is typically repeated numerous times each day to allow the well to resume production.
Conventional bypass or gas-lift plungers are characterized by several inefficiencies, among them slow or erratic operation, inability to tolerate impact and high pressures, susceptibility to rapid wear, failure of clutches used to retain the stem or pushrod or a portion of a valve in position, obstruction of fluid flow or susceptibility to deposits that impede fluid flow through the plunger, etc. Further, some typical plungers are complex, requiring many parts, which usually entails additional operations during manufacturing or repair resulting in higher costs.
For example, any obstruction to the flow of fluid can impede the descent of the plunger. Such obstruction can be rough or protruding features in the flow path, lack of smooth transitions in the flow path, etc. Roughness or other obstructions can accumulate debris, restricting the flow path and cause erratic descent of the plunger. Pins and screws used to retain head and tail pieces or other components to the body portion of the plunger may be sheared when the plunger impacts the bottom of the well bore, for example when the bumper assembly at the well bottom is inoperative or it malfunctions. Screws can loosen if steps are not taken to lock them in place. Clutch assemblies that have several operative components provide additional potential problems if one of the components such as a spring or other part to fail. A clutch malfunction usually means the plunger is disabled, which may require time-consuming procedures to retrieve it from the well bore and a consequent loss of production and increase in operating costs.